But a comprehensive international report released this week charts a guardedly optimistic path to recovery — starting with conservation of an unlikely reef champion — the parrotfish. The report, prepared over three years by 90 experts, was produced by the Global Coral Reef Monitoring Network, the International Union for Conservation of Nature and the United Nations Environment Program (news release).

Coral reef health requires an ecological balance of corals and algae in which herbivory is a key element. Populations of parrotfish are a critical component of that herbivory, particularly since the decline of Diadema sea urchins in the early 1980s; the main causes of mortality of parrotfish are the use of fishing techniques such as spearfishing and, particularly, the use of fish traps…. [M]anagement action to address overfishing at the national and local levels can have a direct positive impact on reef health now and for the future.

The report found no statistically significant evidence of a measurable impact of periods of extreme heat on coral reef fate (search for the phrase “extreme warming events” in the report summary to get the details). [Mark Eakin, a National Oceanic and Atmospheric Administration coral researcher, has a different view, according to an Associated Press story.]

Here’s an excerpt from the report summary capturing the overarching opportunities in shifting fisheries practices and management:

Our results contradict much of the rhetoric about the importance of ocean warming, disease, and hurricanes on coral reefs and emphasize the critical importance of historical perspective for coral reef management and conservation. The threats of climate change and ocean acidification loom increasingly ominously for the future, but local stressors including an explosion in tourism, overfishing, and the resulting increase in macroalgae have been the major drivers of the catastrophic decline of Caribbean corals up until today.

What this means is that smart decisions and actions on a local basis could make an enormous difference for increased resilience and wellbeing of Caribbean coral reefs and the people and enterprises that depend upon them. Thus, four major recommendations emerge from this report:

1. Adopt robust conservation and fisheries management strategies that lead to the restoration of parrotfish populations, including the listing of the parrotfish in relevant annexes of the Protocol concerning Specially Protected Areas and Wildlife of the UNEP Caribbean Environment Program. A recommendation to this effect was passed unanimously at the October 2013 International Coral Reef Initiative Meeting in Belize.

2. Simplify and standardize monitoring of Caribbean reefs and make the results available on an annual basis to facilitate adaptive management.

3. Foster communication and exchange of information so that local authorities can benefit from the experiences of others elsewhere.

4. Develop and implement adaptive legislation and regulations to ensure that threats to coral reefs are systematically addressed, particularly threats posed by fisheries, tourism and coastal development as determined by established indicators of reef health.

Many people say that climate change has already doomed coral reefs. But the report shows that the loss of parrotfishes and other seaweed-eating grazers has been far more important than climate change for Caribbean reef destruction so far. While it is true that climate change poses an enormous risk for the future because of coral bleaching and more acidic oceans, the fact is that reefs protected from overfishing, excessive coastal development and pollution are more resilient to these stresses. Even if we could somehow make climate change disappear tomorrow, these reefs would continue their decline. We must immediately address the grazing problem for the reefs to stand any chance of surviving future climatic shifts.

A companion video accompanying the report also helps tell the story:

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By 2050 or so, the human population is expected to pass nine billion. Those billions will be seeking food, water and other resources on a planet where humans are already shaping climate and the web of life. Dot Earth was created by Andrew Revkin in October 2007 -- in part with support from a John Simon Guggenheim Fellowship -- to explore ways to balance human needs and the planet's limits.